Here's a cool, air-powered simple car that uses similar physics as jet propulsion. It's a good scientific experiment that can be done at home or at school and is at the same time a fun thing to play with.
It teaches the basics of jet propulsion as it uses the same physics but a different type of 'fuel'.
Jet propulsion uses hot gasses shooting out at high pressure to launch a rocket into orbit. In this case, it is air that propels the car forward. When you let it go on the ground, the air inside rushes out of the back and pushes against the front of the balloon. This is known as 'thrust'.
So anyway, this simple car is a great toy to play with, and is good for racing with other balloon cars. I've included a template to record the results of a race if you want to race them in the 'Thanks' step.
Step 1: Materials
Here is what you will need:
- A piece of cardboard measuring 10 cm long by 8 cm wide
- Two pieces of straw trimmed down (without the bendy part) to about 8.2 cm long
- A balloon with the top stiff rubber ring trimmed off
- Another straw trimmed to: Above the bendy part (when extended) 1.7 cm - Below the bendy part (when extended) 5.7 cm
- A skewer trimmed down to two 11.5 cm pieces (You may want to use it to poke the holes in the lids before you trim it - it will ensure the holes are exactly the right size.)
- 4 bottle lids with holes in the centre
Step 2: Attaching the Axles
Attach the two shorter straws (my ones are red) two the back of the piece of cardboard about 1.5 cm from either end. Look at the picture for more detail.
Step 3: Attaching the Axles
Put the skewers inside the straws you attached, and fix the lids onto them. Note that the inside of the lids are facing the outside of the car. You may want to use a scissor to slightly widen the hole up to make it easier to attach the lids. It may also be easier to take out the skewer, attach the lid to one side, then put it back into the straw and put the other lid on.
Step 4: The Balloon 'Engine'
Grab the other straw (mine is yellow) and put it into the balloon (the shorter side) until the edge of the balloon touches the beginning of the bendy part. Twist it on to make sure it is airtight and sticky-tape it together. Blow into the long end of the straw to ensure the seal is airtight and the balloon inflates properly.
Step 5: Attaching the Balloon to the Car
Finally, attach the balloon to the car like shown in the image. The end of the bendy part should be touching the end of the cardboard.
Step 6: You're Done!
You're done. Now blow the balloon up, bend the end of the straw so air can't escape until you put it on the ground. Once it is on a flat surface, let it go! Try playing with balloons of different sizes, and try putting up ramps!
You can also add stickers and any other sort of decorations like a seat, wheel and maybe even a roof. Be creative!
Step 7: Thanks!
Here is the racing data sheet.
And of course, thanks for reading. I hope you enjoyed it. Please comment and share and post a pic of your car in the comments!